1. Field of the Invention
The invention relates to an apparatus for the intermediate storage of a strap to be supplied and delivered discontinuously in a machine, in particular for a looping strap in a packaging machine.
2. Background Art
Intermediate stores of the generic type are needed primarily--but not exclusively--in today's packaging and looping machines, where a strap is taken off a comparatively bulky supply coil on the one hand and inserted into the packaging machine at a very high speed of as many as several meters per second on the other hand. Due to this high speed, the strap cannot be taken directly off the coil since this would imply an acceleration of the supply coil that cannot be put into practice accompanied with virtually non-transferable driving forces to act on the strap.
Another problem in particular with looping machines resides in the fact that the strap is slung as a loose noose from a strap supply around the product stack to be looped. The leading end of the strap is then fixed in the looping machine and the noose is tightened. The section of the strap thus pulled back must be kept adequately so that any trouble in the operation of the machine for instance by an entwined or entangled strap be avoided. To this end, there must be the possibility of pushing or pulling the strap back preferably into the intermediate store.
For these reasons intermediate stores are used, in which the strap is kept in a more or less loose and regular arrangement. One type of such an intermediate store can be seen for example in DE-PS 29 35 894, where the packaging strap is stored in freely meandering loops one above the other. The drawback resides in that the strap curves by a very small radius at the summits of the loops in particular when the store is densely packed. When the strap is kept in the intermediate store for a prolonged time--for instance in the case of breaks in the operation of the packaging machine--this curving engages itself on the strap, which may lead to problems in the subsequent handling of the strap in the machine.
To avoid this drawback, EP 0 139 088 B1 proposes an intermediate store consisting of a flat drum in the form of a cylindrical disk in which the packaging strap is coiled, spiraling loosely. Supply of the strap takes place from the side to the innermost turn at a very acute angle relative to the plane of the drum, delivery takes place starting from the outermost turn of the coil via a gap in the peripheral outer wall of the drum.
The known prior art has the drawback of the comparatively complicated guidance of the strap towards the coil for the strap to approach the innermost turn. Since the turns of the packaging strap lie freely one above the other, the individual layers of the coil of strap may interact, which may give rise to problems in particular in the case of a high level of filling of the store. This applies especially to the specific application in a looping machine, where the strap, when inserted into the strap guiding frame, must be pulled back during the looping job and pushed back into the intermediate store also from the delivery side.